(a) Field of the Invention
The present invention relates to a method for controlling a shifting during shifting, defined as a frictional element being re-engaged in mid-course of being released, and a system thereof. More particularly, the present invention relates to a method for controlling a shifting during shifting and a system thereof that reduce shift shock by prohibiting a pre-charge in the case of shifting during shifting.
(b) Description of the Related Art
Generally, an automatic transmission shifts to a target shift speed, derived from a predetermined shifting pattern based on vehicle speed and variation of a throttle opening. Operational elements are controlled according to a hydraulic duty of the target shift speed.
During shifting, an off-going element is released from an engaged state and an on-coming element is engaged from a released state. Releasing an off-going element and engaging an on-coming element are achieved by controlling hydraulic pressure supplied to the elements.
To engage the on-coming element, a transmission control unit receives a shifting signal, and drives an actuator such that a hydraulic pressure of the on-coming element is quickly raised to a pre-charge pressure, at which it is maintained for a predetermined time. This is for quickly engaging the on-coming element.
After that, the transmission control unit quickly reduces the hydraulic pressure of the on-coming element and then gradually increases the hydraulic pressure of the on-coming element with a predetermined gradient. The hydraulic pressure applied at this state is called a stand-by pressure.
The above described method is also traditionally used to control engagement of the on-coming element of shifting during shifting, in which a frictional element is re-engaged in mid-course of being released. Therefore, shift shock may occur at a pre-charge process as a consequence of residual control pressure of a previous shift.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.